Editing Tupolev Tu-144 (section)

==Design==
Along with early [[Tupolev Tu-134|Tu-134s]], the Tu-144 was one of the last commercial aircraft with a [[braking parachute]]. The Tu-144 was not fitted with any reverse thrust capabilities, and so the parachute was used as the sole alternative.<ref name="bbc-20171018" /> A prototype without passenger seats was fitted with [[ejection seat]]s for pilots.<ref>{{cite magazine |title=Ramenskoye, Past and Present |magazine=Air Force Magazine |date=April 2008 |page=53 |url=https://books.google.com/books?id=uUHUMGqFoagC&pg=RA3-PA53 |access-date=25 February 2023 |archive-date=29 September 2023 |archive-url=https://web.archive.org/web/20230929162302/https://books.google.com/books?id=uUHUMGqFoagC&pg=RA3-PA53 |url-status=live }}</ref>

;Materials:
The aircraft was designed for a 30,000-hour service life over 15 years. Airframe heating and the high temperature properties of the primary structural materials, which were [[aluminium alloy]]s, set the maximum speed at Mach 2.2.<ref name="GordonKomissarovRigmant2015" />{{rp|page=49}} 15% by weight was [[titanium]] and 23% non-metallic materials. Titanium or stainless steel were used for the leading edges, elevons, rudder and the rear fuselage engine-exhaust [[heat shield]].<ref name="NASA Tu-144LL" />

===Engines===
[[File:Tupolev Tu-144 AN0521445.jpg|thumb|Afterburning nozzles on the Kuznetsov turbofan.]]
[[File:Tupolev Tu-144 at the MAKS-2013 (05).jpg|thumb|Plug nozzles on the non-afterburning Kolesov turbojet.]]

SSTs for M2.2 had been designed in the Soviet Union before Tupolev was tasked with developing one. Design studies for the [[Myasishchev]] SST had shown that a cruise [[Thrust specific fuel consumption|specific fuel consumption]] (SFC) of not more than 1.2&nbsp;kg/kgp hr would be required.<ref name="tupolev.ru"/> The only engine available in time with the required thrust and suitable for testing and perfecting the aircraft was the [[afterburning]] [[Kuznetsov NK-144]] [[turbofan]] with a cruise SFC of 1.58&nbsp;kg/kgp hr. Development of an alternative engine to meet the SFC requirement, a non-afterburning turbojet, the [[Kolesov RD-36-51]]A, began in 1964.<ref name="tupolev.ru" /> It took a long time for this engine to achieve acceptable SFC and reliability.<ref name="GordonKomissarovRigmant2015" />{{rp|page=42}} In the meantime the NK-144 high SFC gave a limited [[range (aeronautics)|range]] of about {{convert|2500|km|mi nmi|abbr=on|lk=out}}, far less than Concorde. A maximum speed of {{convert|2443|km/h|mph kn|abbr=on}} (Mach 2.35) was reached with afterburning.<ref name="GordonKomissarovRigmant2015" /> Afterburners were added to Concorde to meet its take-off thrust requirement<ref>Not Much of an Engineer, Sir Stanley Hooker, Airlife Publishing 2002, {{ISBN|978-1853102851}}, p. 153</ref> and were not necessary for supersonic cruise; the Tu-144 used maximum afterburner for take-off and minimum for cruise.<ref name="GordonKomissarovRigmant2015" />{{rp|page=110}}

The '''Tu-144S''', of which nine were produced, was fitted with the [[Kuznetsov NK-144]]A [[turbofan]] to address lack of take-off thrust and surge margin. SFC at M2.0 was 1.81&nbsp;kg/kgp hr. A further improvement, the NK-144V, achieved the required SFC, but too late to influence the decision to use the [[Kolesov RD-36-51]].<ref name="GordonKomissarovRigmant2015" />{{rp|page=135}}

The '''Tu-144D''', of which five were produced (plus one uncompleted), was powered by the [[Kolesov RD-36-51]] turbojet with an SFC of 1.22&nbsp;kg/kgp hr. The range with full payload increased to 5,330&nbsp;km compared to 6,470&nbsp;km for Concorde.<ref name="GordonKomissarovRigmant2015" />{{rp|page=248}} Plans for an aircraft with a range in excess of {{convert|7000|km|mi nmi|abbr=on}} range were never implemented.<ref name="tupolev.ru" />

The engine intakes had variable [[intake ramp]]s and bypass flaps with positions controlled automatically to suit the engine airflow.<ref name="tupolev.ru"/> They were very long to help prevent surging;<ref name="GordonKomissarovRigmant2015" />{{rp|page=131}} twice as long as those on Concorde. Jean Rech (Sud Aviation) states the need for excessive length was based on the misconception that length was required to attenuate [[intake]] distortion.<ref name="Owen2002">{{cite book |editor1-last=Owen |editor1-first=Kenneth |title=Concorde |date=2002 |publisher=Institute of Contemporary British History |location=London |isbn=0-9523210-7-6 |url=https://www.kcl.ac.uk/sspp/assets/icbh-witness/concorde.pdf |page=90 |archive-url=https://web.archive.org/web/20230531031823/https://www.kcl.ac.uk/sspp/assets/icbh-witness/concorde.pdf |archive-date=31 May 2023 |url-status=live }}</ref> The intakes were to be shortened by 10 feet on the projected '''Tu-144M'''.<ref name="GordonKomissarovRigmant2015" />{{rp|page=178}}

The [[Kolesov RD-36-51]] had an unusual translating plug nozzle as an alternative to a variable con-di nozzle, either of which give the variable area ratio required for the range of nozzle pressures which come from low inlet ram at low speeds to high at Mach 2. A plug nozzle was studied for [[Concorde]] but rejected as it was not certain that it could be cooled adequately during afterburner operation.<ref>https://arc.aiaa.org/doi/book/10.2514/4.868122, p.6-1</ref> The RD-36-51 had no afterburner.

===Airframe===
[[File:Tupolev Tu-144S, Aeroflot AN1180630.jpg|thumb| Tail surfaces or [[empennage]] showing deflected rudder and no horizontal tailplane.]]
[[File:Tupolev Tu-144 CCCP-77102 LEB 02.06.73 edited-3.jpg|thumb|right|The first production Tu-144S displaying at the 1973 [[Paris Air Show]] on the day before it crashed. The aircraft's planform and canards are clearly shown.]]
The aircraft was assembled from parts machined from large slabs, many over {{convert|19|m|ft|abbr=on}} long and {{convert|0.64|to|1.27|m|ft|abbr=on}} wide. While at the time, this approach was heralded as an advanced feature of the design, it turned out that finished parts contained defects which had not been detected in the [[raw material]]. Cracks formed at the defects at load levels below that which the part was expected to withstand. Once a crack started to grow, it spread quickly over many metres, with no crack-arresting design feature to stop it.<ref name="Fridlyander"/> In 1976, during [[Fatigue testing|repeat-load]] and [[Proof test|static testing]] at [[TsAGI]] (Russia's ''Central Aerohydrodynamic Institute''), a Tu-144S airframe cracked at 70% of the design flight load with cracks running many metres in both directions from their origin.<ref name="bliznyuk2000" /><ref name="Fridlyander"/>

Two Tu-144S airframes suffered structural failures during laboratory testing just prior to the Tu-144 entering passenger service.<ref name="Fridlyander">{{cite journal |last=Fridlyander |first=Iosif Naumovich |title=Печальная эпопея Ту-144 |trans-title=Sad Epic of the Tu-144 |journal=Messenger of Russian Academy of Sciences |year=2002 |volume=72 |issue=1 |pages=70–78 |url=http://vivovoco.rsl.ru/VV/JOURNAL/VRAN/02_01/FRID.HTM |archive-url=https://web.archive.org/web/20110928042757/http://vivovoco.rsl.ru/VV/JOURNAL/VRAN/02_01/FRID.HTM |archive-date=28 September 2011 |language=ru |url-status=dead }}</ref> The problem, discovered in 1976, may have been known prior to this testing; a large crack was discovered in the airframe of the prototype Tu-144 (aircraft 68001) during a stopover in Warsaw following its appearance at the 1971 Paris Air Show. Polish sources say the crack was discovered after the aircraft made an emergency landing due to the failure of both left-hand engines; however, an Aeroflot spokesperson denied the damage and disputed the circumstances of the landing.{{sfn|Moon|1989|p=141}}

Later the same year, a test airframe was subjected to a test simulating the temperatures and pressures occurring during a flight. High skin temperatures of {{convert|110|-|130|C|F|abbr=on|sigfig=2}} were caused by kinetic heating when the boundary layer air reached {{convert|150|-|180|C|F|abbr=on|sigfig=2}} during cruise. The Tu-144 was placed in an [[environmental chamber]] and heated to simulate the skin getting hot quickly, during acceleration to cruising speed, while the underlying structure took a while to reach its equilibrium temperature. This thermal effect caused internal stresses and the situation was reversed while slowing down and descending. The pressure in the cabin, which caused additional stresses, was changed at the same time as the skin heating to simulate climbing to cruise altitude and then descending. Repeatedly cycling the temperature and pressure, as happened with the aircraft in service, caused fatigue damage<ref>Tupolev Tu-144 The Soviet Supersonic Airliner,{{ISBN|978-0-7643-4894-5}}, pp.48,61</ref> and the airframe failed in a similar way to that of the TsAGI load testing.<ref name="bliznyuk2000" /><ref name="Fridlyander"/>

According to {{ill|Iosif Fridlyander|ru|Фридляндер, Иосиф Наумович}}, an aerospace aluminium and beryllium alloys expert,<ref name="AyzatullovaSudakov2020">{{cite journal |last1=Ayzatullova |first1=Alsu Sh. |last2=Sudakov |first2=Mikhail A. |title=История создания и эксплуатации сверхзвукового пассажирского самолёта Ту-144 (по мемуарным источникам) |trans-title=The History of the Creation and Operation of the TU-144 Supersonic Airliner (According to Memoir Sources) |journal=Vestnik of Kostroma State University |date=2020 |volume=26 |issue=3 |pages=87–92 |url=https://vestnik.ksu.edu.ru/2020-t-26-3/ayzatullova-as-sudakov-ma-vestnik-2020-3-ru.html |archive-url=https://web.archive.org/web/20230607000522/https://vestnik.ksu.edu.ru/2020-t-26-3/ayzatullova-as-sudakov-ma-vestnik-2020-3-ru.html |archive-date=7 June 2023 |url-status=live |doi=10.34216/1998-0817-2020-26-3-87-92 |doi-access=free |language=ru}}</ref>{{rp|page=88}} the Tu-144 design allowed a higher incidence of defects in the alloy structure, leading to the fatal in-air breakup of the aircraft in the [[1973 Paris Air Show Tu-144 crash]].<ref name="AyzatullovaSudakov2020" />{{rp|page=91}} This conclusion was supported by some of the designers involved in the aircraft's development. Vadim Razumikhin wrote that the [[Load factor (aeronautics)|load factor]] experienced by the plane at the moment of the break-up was less than the design limit. If the stress tests had been conducted earlier, the disaster may have been averted. Eventually, the airframe was strengthened and the control system was modified to prevent overstressing the aircraft.<ref name="bliznyuk2000" />{{rp|at=Ch. 3.14.}}